A semiconductor relay (optical semiconductor relay device) is one type of a relay having no movable contact (which is a non-contact relay), and is a relay that inputs/outputs signals by an electronic circuit using a semiconductor. As such a semiconductor relay, for example, a so-called solid state relay is cited. In the solid state relay, non-contact signal transmission is achieved by signal transmission using an optical signal and an electric signal in an electrically-insulated space between a light-emitting element such as a photo coupler and a semiconductor element (semiconductor device) such as a thyristor, triac, diode, and transistor.
For example, Patent Document 1 (Japanese Patent Application Laid-Open Publication No. H04-303973) disclose a technique of covering surfaces of a photovoltaic diode and a control circuit with a polycrystalline semiconductor layer in a photo acceptance element for the solid state relay.